This invention relates to the testing of a lens, and more particularly concerns a method and apparatus for verifying the power of an intraocular lens immediately prior to its implantation into a patient's eye.
Intraocular lenses of glass or polymethyl methacrylate are manufactured by a number of different companies. It has been found that a significant percentage of the lenses are mislabeled or are optically aberrant. Accordingly, concientious ophthalmic surgeons strive to verify the characteristics of the lens prior to implantation into the patient's eye. The most significant feature of the lens requiring verification is its power as measured in terms of diopters. A lens having a focal length of 1 meter has a power of 1 diopter. The power (P) of a lens in diopters may be expressed as: EQU P=1/f
where f is the focal length of the lens in meters. Diverging lenses are designated negative lenses, and converging lenses are termed positive lenses. To be acceptable for use, an intraocular lens should test within .+-.0.5 diopter of its stated power.
Although earlier devices have been known for testing intraocular lenses, such devices, most requiring use of a lensometer, are expensive, time consuming, or incompatible with the sterile requirements of the operating room. Also, some of the earlier testing systems are limited to testing of the lens in either air or aqueous immersion.
It is accordingly an object of the present invention to provide a method for quickly and accurately testing the power of intraocular lenses under sterile conditions.
It is another object of this invention to provide an easily manipulated and easily sterilizable apparatus useful in carrying out the test method of the foregoing object.
It is a further object of the present invention to provide an apparatus of the aforesaid nature capable of providing test results in air.
It is still another object of this invention to provide an improved lens testing apparatus of the aforesaid nature of simple and rugged construction which may be economically manufactured.
These objects and other objects and advantages of the invention will be apparent from the following description.